This invention relates to a process for subbing a photographic hydrophobic film. More particularly, the invention pertains to a process for subbing a photographic hydrophobic film in order to improve adhesion of a light-sensitive photographic layer which is coated on the hydrophobic film to form a light-sensitive composite photographic material, especially in order to improve the resulting light-sensitive materials ability to resist edge-peeling in a treating bath. The process comprises applying, on the surface of the hydrophobic film, an aqueous dispersion containing a copolymer comprising, as the main components, (1) glycidyl methacrylate and/or glycidyl acrylate and (2) a compound of the general formula ##STR1##
It is difficult to obtain satisfactory adhesion between a hydrophilic material such as gelatin, and a hydrophobic support surface because of the lack of affinity between said material and said surface. Even if a coating can be formed on the hydrophobic surface, the adhesion is weak and, consequently, the hydrophobic material tends to peel off from the hydrophobic support.
Accordingly, it has heretofore been common practice to subject at least one surface of a hydrophobic support to a subbing treatment before applying the coating material.
However, in a light-sensitive photographic material, it is necessary to make the hydrophilic material adhere strongly to the hydrophobic support since the photographic material is treated under a variety of conditions. For example, the photographic film must be wet during the development treatment and dry before and after the development treatment.
Therefore, attempts have been made to improve adhesion between the hydrophilic material and the support. For instance, a vinylidene type terpolymer containing an acid moiety having an affinity for both a support film and a light-sensitive photographic layer or a polymer obtained by grafting a butyl acrylate/styrene copolymer on gelatin or a butadiene type polymer is dissolved, for example, in ethylene chloride, dioxane, acetone or methyl alcohol is used to form a solution. The resulting solution is added to an organic solvent such as chlorophenol or cresol which acts as a solvent or swelling agent for the support film then, this solution is coated on the surface of the substrate in order to obtain greater adhesion between the support film and the light-sensitive photograhic layer.
The disadvantage of the above-mentioned method involves the use of the solvent type subbing liquid which releases a vapor when dried which is harmful to the environment. Additionally, the subbed film eventually fails to maintain its transparent appearance as well as its flatness. This results in noticeable degradation of the resulting subbed film.
Under such circumstances, there is adopted, for example, a method wherein the suppprt film is coated (before stretching or after monoaxial stretching but before biaxial stretching thereof) on the surface with a solvent type subbing liquid which does not contain a solvent or swelling agent for the support film. This method is disadvantageous because a large amount of the perimeter material must be discarded due to the waste material formed by stretching the support film.
In order to overcome this drawback there is a method in which an aqueous dispersion containing a copolymer obtained from various monomers is used as a subbing liquid in place of the aforesaid solvent type subbing liquid. For example, U.S. Pat. No. 3,615,556 discloses a subbing process in which a biaxially stretched polyester film is coated with an aqueous dispersion containing a butadiene/styrene copolymer having an acid moiety.
U.S. Pat. No. 2,627,088 and 2,698,240, respectively disclose a process in which, prior to stretching, a polyester film is subbed on the surface with an aqueous dispersion containing a vinylidene type copolymer having an acid moiety. Further, Japanese Patent Publications Nos. 13278/1969 and 10988/1970, respectively disclose a process in which the surface of a biaxially stretched polyester film is coated with an aqueous dispersion containing a copolymer obtained from an alkyl acrylate and an aliphatic bifunctional monomer having two allyl or vinyl groups. However, it is difficult to properly select the aqueous dispersion and subbing conditions necessary to achieve excellent adhesion.
On the other hand, a process has been proposed which subjects a hydrophobic film to pretreatment rendering the surface hydrophilic. Examples of the pretreatment include corona discharge and ultraviolet irradiation. Subsequently, the pretreated surface of the film is coated with a subbing liquid.
The adhesion of the hydropholic layer to the hydrophobic film has been greatly improved by application of this process to the aforesaid subbing process using an aqueous copolymer dispersion. For instance, Japanese Laid-Open-to-Public Publication No. 11118/1974 discloses a light-sensitive silver halide photogrphic material obtained by coating a silver halide emulsion layer on a polyester film support which had been previously pretretreated to render it hydrophilic. The surface of the film support is coated with an aqueous copolymer dispersion. The resulting film exhibited excellent adhesion from its initial preparation to the drying stage subsequent to development.
However, the photographic material prepared as described above does not exhibit satisfactory results with regard to edge peeling when the photographic material was subjected to development by means of an automatic developing machine. The term "edge-peeling" refers to the peeling of the silver halide emulsion layer when the edges of said layer are rubbed with a finger or piece of soft rubber during the development of a light-sensitive silver halide photographic material while wet.
The problems associated with edge peeling arise, for example, when a light-sensitive silver halide photographic material is developed by means of an automatic developing machine and is rubbed with a travelling rack or rubber roll. The silver halide emulsion layer formed thereon peels from the perimeter portions of said photographic material. This results in significant deterioration of the quality of the developed photographic material. Further, the prior art subbing processes using an aqueous dispersion type subbing liquid provide unsatisfactory results because of the occurrence of the so-called blocking phenomenon. This results from the incorporation of a surface active agent and a polymerization initiator into the aqueous copolymer dispersion. Some of these components find their way into the resulting sub layer which results in the formation of creases on the subbed support film prior to coating on the subbed layer.
Thus, there is a need in the photographic art to obtain a subbing process that provides adequate adhesion between the film support and the light-sensitive layer. Additionally, the resulting photographic material must resist edge-peeling and the so-called blocking phenomenon. An object of the present invention is to provide a subbing process for light-sensitive photographic materials using, as supports, highly hydrophobic films. For example, such supports include polyesters such as polyethylene terephthalate, polyethylene-2,6-naphthalate or poly(cyclohexane-1,4-dimethanolterephthalic acid ester), cellulose esters such as cellulose diacetate or cellulose triacetate, and polycarbonate. The present subbing process eliminates the discharge of harmful organic solvent vapors and results in a material having excellent adhesion and edge-peeling resistance. Additionally, the blocking phenomenon is eliminated which occurs after coating and drying a subbing liquid on the support and before coating a subsequent layer on the subbed surface of the support.
More particularly, the present invention provides a subbing process in which edge-peeling is eliminated from a light-sensitive silver halide photograpic material comprising a hydrophobic film as support which is pretreated.